Teflon is Polytetrafluoroetylene, referred to as Teflon, PTFE, F4, etc.It is also known as Teflon, Teflon, Teflon, Teflon and so on because of its pronunciation.Polytetrafluoroethylene (ptfe) is a kind of plastic, which is used to manufacture heaters. It has been successfully used in chemical equipment heating. It has the characteristics of multi-layer and three-dimensional heating.
The working pressure, working temperature, heat transfer coefficient and installation method of the teflon heater vary greatly according to different types, different shell materials and different thermal media.The chemical properties of teflon are very stable and the corrosion resistance is especially good.The surface of the teflon tube is smooth and moderately flexible, so it is not easy to scale due to the slight vibration when using it.The teflon heater is small in size and compact in structure. The heat transfer area per unit volume of the equipment is more than 4 times of that of the shell heater.Flexible teflon tubes work safely under shock and vibration of fluids, and the tubes can be made into special shapes as needed.Teflon has low thermal conductivity, poor mechanical properties than metal, and is not resistant to high temperature.The use of small diameter, thin wall, although the thermal conductivity and mechanical properties of compensation, but can only be used in the case of low pressure and low temperature.The production of teflon steam heater and teflon hot water heater has become more and more mature, and widely used in chemical industry, medicine, pickling and other corrosive industries.
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How to verify the pressure transmitter
The pressure transmitter is a commonly used measuring instrument, which can convert the physical parameters such as gas and liquid felt by the pressure measuring component into standard signal output, and has the advantages of accurate measurement, stable performance, high sensitivity and easy operation. When the user uses the product to verify the normal operation of the pressure transmitter, the pressure transmitter needs to be verified.
First, the true calibration of the pressure transmitter requires a standard pressure source to be input to the transmitter. Since the range (LRV, URV) is not calibrated without the use of a standard, ignoring the input section (pressure input to the transmitter) for output regulation (transfer circuitry of the transmitter) is not the correct calibration.
Furthermore, the relationship between the pressure and differential pressure detecting components, the A/D conversion circuit, and the current output is not equal. The purpose of the calibration is to find the relationship between the three. The pressure source is connected to the self-made joint through the rubber tube, the balance valve is closed, and the air circuit sealing condition is checked, and then the ammeter (voltmeter) and the hand-held device are connected into the output circuit of the transmitter, and the calibration is started after the power is preheated. We know that no matter what type of differential pressure transmitter, the positive and negative pressure chambers have exhaust, drain valve or cock; this is convenient for us to calibrate the differential pressure transmitter on site, that is to say, it is not necessary to remove the guide. The differential pressure transmitter can be calibrated by the pressure tube. When calibrating the differential pressure transmitter, first close the positive and negative valves of the three-valve group, open the balance valve, and then loosen the exhaust, drain valve or cock to empty, and then replace the positive pressure chamber with a self-made joint. The exhaust, drain valve or cock; while the negative pressure chamber remains loose, allowing it to pass through the atmosphere.
First adjust the damping to zero state, first adjust the zero point, then adjust the full scale pressure to full scale, so that the output is 20mA, the on-site adjustment is fast, here introduces the zero adjustment of the zero point and range. Zero adjustment has almost no effect on fullness, but the fullness has an effect on zero. When there is no migration, the effect is about 1/5 of the range adjustment, that is, the range is adjusted upward by 1 mA, and the zero point will move upward by about 0.2 mA. ,vice versa. It is not acceptable to calibrate the smart transmitter using the conventional method described above, as this is determined by the structural principle of the HART transmitter. Because the smart transmitter is between the input pressure source and the generated 4-20 mA current signal, in addition to the mechanical and electrical circuits, there is also the operation of the microprocessor chip on the input data. Therefore, the adjustment is different from the conventional method.
The actual pressure transmitter can be calibrated as follows:
1. Make a 4-20 mA trimming to correct the D/A converter inside the transmitter. Since it does not involve sensing components, no external pressure source is required.
2. Perform a full fine-tuning to match the 4-20 mA, digital reading to the actual applied pressure signal, thus requiring a pressure source.